Mist inhaler devices

ABSTRACT

A mist inhaler device ( 200 ) for generating a mist for inhalation by a user. The device includes a mist generator device ( 201 ) and a driver device ( 202 ). The driver device ( 202 ) is configured to drive the mist generator device ( 201 ) at an optimum frequency to maximise the efficiency of mist generation by the mist generator device ( 201 ).

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 17/837,995, filed Jun. 10, 2022, which is a continuation of U.S.patent application Ser. No. 17/122,025, filed Dec. 15, 2020, whichclaims the benefit of priority to and incorporates by reference hereinthe entirety of each of: International patent application no.PCT/IB2019/060808, filed on Dec. 15, 2019; International patentapplication no. PCT/IB2019/060810, filed on Dec. 15, 2019; Internationalpatent application no. PCT/IB2019/060811, filed on Dec. 15, 2019;International patent application no. PCT/IB2019/060812, filed on Dec.15, 2019; European patent application no. 20168245.7, filed on Apr. 6,2020; European patent application no. 20168231.7, filed on 6 Apr. 2020;and European patent application no. 20168938.7, filed on Apr. 9, 2020.

FIELD

The present invention relates to mist inhaler devices. The presentinvention more particularly relates to ultrasonic mist inhaler devicesfor atomising a liquid by ultrasonic vibrations.

BACKGROUND

Mist inhaler devices are used for generating a mist or vapour forinhalation by a user. The mist may contain a drug or medicine which isinhaled by a user and absorbed into the user's blood stream.

In particular, mist inhaler devices or electronic vaporising inhalersare becoming popular among smokers who want to avoid the tar and otherharsh chemicals associated with traditional cigarettes and who wish tosatisfy the craving for nicotine. Electronic vaporising inhalers maycontain liquid nicotine, which is typically a mixture of nicotine oil, asolvent, water, and often flavouring. When the user draws, or inhales,on the electronic vaporising inhaler, the liquid nicotine is drawn intoa vaporiser where it is heated into a vapour. As the user draws on theelectronic vaporising inhaler, the vapour containing the nicotine isinhaled. Such electronic vaporising inhalers may have medical purpose.

Electronic vaporising inhalers and other vapour inhalers typically havesimilar designs. Most electronic vaporising inhalers feature a liquidnicotine reservoir with an interior membrane, such as a capillaryelement, typically cotton, that holds the liquid nicotine so as toprevent leaking from the reservoir. Nevertheless, these cigarettes arestill prone to leaking because there is no obstacle to prevent theliquid from flowing out of the membrane and into the mouthpiece. Aleaking electronic vaporising inhaler is problematic for severalreasons. As a first disadvantage, the liquid can leak into theelectronic components, which can cause serious damage to the device. Asa second disadvantage, the liquid can leak into the electronicvaporising inhaler mouthpiece, and the user may inhale the unvapourisedliquid.

Electronic vaporising inhalers are also known for providing inconsistentdoses between draws. The aforementioned leaking is one cause ofinconsistent doses because the membrane may be oversaturated orundersaturated near the vaporiser. If the membrane is oversaturated,then the user may experience a stronger than desired dose of vapour, andif the membrane is undersaturated, then the user may experience a weakerthan desired dose of vapour. Additionally, small changes in the strengthof the user's draw may provide stronger or weaker doses. Inconsistentdosing, along with leaking, can lead to faster consumption of the vapingliquid.

Additionally, conventional electronic vaporising inhalers tend to relyon inducing high temperatures of a metal heating component configured toheat a liquid in the e-cigarette, thus vaporising the liquid that can bebreathed in. Problems with conventional electronic vaporising inhalersmay include the possibility of burning metal and subsequent breathing inof the metal along with the burnt liquid. In addition, some may notprefer the burnt smell caused by the heated liquid.

Thus, a need exists in the art for improved mist inhaler devices whichseek to address at least some of the problems described herein.

SUMMARY

According to one aspect, there is provided a mist inhaler device forgenerating a mist for inhalation by a user, the device comprising:

-   -   a mist generator device which incorporates:        -   a mist generator housing which is elongate and comprises an            air inlet port and a mist outlet port;        -   a liquid chamber provided within the mist generator housing,            the liquid chamber for containing a liquid to be atomised;        -   a sonication chamber provided within the mist generator            housing;        -   a capillary element extending between the liquid chamber and            the sonication chamber such that a first portion of the            capillary element is within the liquid chamber and a second            portion of the capillary element is within the sonication            chamber;        -   an ultrasonic transducer having a generally planar            atomisation surface which is provided within the sonication            chamber, the ultrasonic transducer being mounted within the            mist generator housing such that the plane of the            atomisation surface is substantially parallel with a            longitudinal length of the mist generator housing, wherein            part of the second portion of the capillary element is            superimposed on part of the atomisation surface, and wherein            the ultrasonic transducer is configured to vibrate the            atomisation surface to atomise a liquid carried by the            second portion of the capillary element to generate a mist            comprising the atomised liquid and air within the sonication            chamber; and        -   an airflow arrangement which provides an air flow path            between the air inlet port, the sonication chamber and the            air outlet port such that a user drawing on the mist outlet            port draws air through the inlet port, through the            sonication chamber and out through the mist outlet port,            with the mist generated in the sonication chamber being            carried by the air out through the mist outlet port for            inhalation by the user, wherein the mist inhaler device            further comprises:            a driver device which incorporates:    -   a battery;    -   an AC driver for converting a voltage from the battery into an        AC drive signal at a predetermined frequency to drive the        ultrasonic transducer;    -   an active power monitoring arrangement for monitoring the active        power used by the ultrasonic transducer when the ultrasonic        transducer is driven by the AC drive signal, wherein the active        power monitoring arrangement provides a monitoring signal which        is indicative of an active power used by the ultrasonic        transducer;    -   a processor for controlling the AC driver and for receiving the        monitoring signal drive from the active power monitoring        arrangement; and    -   a memory storing instructions which, when executed by the        processor, cause the processor to:    -   A. control the AC driver to output an AC drive signal to the        ultrasonic transducer at a predetermined sweep frequency;    -   B. calculate the active power being used by the ultrasonic        transducer based on the monitoring signal;    -   C. control the AC driver to modulate the AC drive signal to        maximise the active power being used by the ultrasonic        transducer;    -   D. store a record in the memory of the maximum active power used        by the ultrasonic transducer and the sweep frequency of the AC        drive signal;    -   E. repeat steps A-D for a predetermined number of iterations        with the sweep frequency incrementing with each iteration such        that, after the predetermined number of iterations has occurred,        the sweep frequency has been incremented from a start sweep        frequency to an end sweep frequency;    -   F. identify from the records stored in the memory the optimum        frequency for the AC drive signal which is the sweep frequency        of the AC drive signal at which a maximum active power is used        by the ultrasonic transducer; and    -   G. control the AC driver to output an AC drive signal to the        ultrasonic transducer at the optimum frequency to drive the        ultrasonic transducer to atomise a liquid.

In some examples, the driver device is releasably attached to the mistgenerator device such that the driver device is separable from the mistgenerator device.

According to another aspect, there is provided a mist generator devicewhich incorporates:

-   -   a mist generator housing which is elongate and comprises an air        inlet port and a mist outlet port;    -   a liquid chamber provided within the mist generator housing, the        liquid chamber for containing a liquid to be atomised;    -   a sonication chamber provided within the mist generator housing;    -   a capillary element extending between the liquid chamber and the        sonication chamber such that a first portion of the capillary        element is within the liquid chamber and a second portion of the        capillary element is within the sonication chamber;    -   an ultrasonic transducer having a generally planar atomisation        surface which is provided within the sonication chamber, the        ultrasonic transducer being mounted within the mist generator        housing such that the plane of the atomisation surface is        substantially parallel with a longitudinal length of the mist        generator housing, wherein part of the second portion of the        capillary element is superimposed on part of the atomisation        surface, and wherein the ultrasonic transducer is configured to        vibrate the atomisation surface to atomise a liquid carried by        the second portion of the capillary element to generate a mist        comprising the atomised liquid and air within the sonication        chamber, and    -   an airflow arrangement which provides an air flow path between        the air inlet port, the sonication chamber and the air outlet        port such that a user drawing on the mist outlet port draws air        through the inlet port, through the sonication chamber and out        through the mist outlet port, with the mist generated in the        sonication chamber being carried by the air out through the mist        outlet port for inhalation by the user.

In some examples, the mist generator device further comprises: atransducer holder which is held within the mist generator housing, thetransducer element holds the ultrasonic transducer and retains thesecond portion of the capillary element superimposed on part of theatomisation surface; and a divider portion which provides a barrierbetween the liquid chamber and the sonication chamber, wherein thedivider portion comprises a capillary aperture through which part of thefirst portion of the capillary element extends.

In some examples, the transducer holder is of liquid silicone rubber.

In some examples, the liquid silicone rubber has a Shore A 60 hardness.

In some examples, the capillary aperture is an elongate slot having awidth of 0.2 mm to 0.4 mm.

In some examples, the capillary element is generally planar with firstportion having a generally rectangular shape and the second portionhaving a partly circular in shape.

In some examples, the capillary element has a thickness of substantially0.28 mm.

In some examples, the capillary element comprises a first part and asecond part which are superimposed on one another such that thecapillary element has two layers.

In some examples, the capillary element is of at least 75% bamboo fibre.

In some examples, the capillary element is 100% bamboo fibre.

In some examples, the airflow arrangement is configured to change thedirection of a flow of air along the air flow path such that the flow ofair is substantially perpendicular to the atomisation surface of theultrasonic transducer as the flow of air passes into the sonicationchamber.

In some examples, the change of direction of the flow of air issubstantially 90°.

In some examples, the airflow arrangement provides an air flow pathhaving an average cross-sectional area of substantially 11.5 mm².

In some examples, the mist generator device further comprises: at leastone absorbent element which is provided adjacent the mist outlet port toabsorb liquid at the mist outlet port.

In some examples, each absorbent element is of bamboo fibre.

In some examples, the mist generator housing is at least partly of aheterophasic copolymer.

In some examples, the heterophasic copolymer is polypropylene.

In some examples, the ultrasonic transducer is circular and has adiameter of substantially 16 mm.

In some examples, the liquid chamber contains a liquid having a liquidviscosity between 1.05 Pa·s and 1.412 Pa·s and a liquid density between1.1 g/ml and 1.3 g/ml.

In some examples, the liquid chamber contains a liquid comprising anicotine levulinate salt at a 1:1 molar ratio.

In some examples, the mist generator device further comprises: anidentification arrangement which is provided on the mist generatorhousing, the identification arrangement comprising: an integratedcircuit having a memory which stores a unique identifier for the mistgenerator device; and an electrical connection which provides anelectronic interface for communication with the integrated circuit.

In some examples, the memory of the integrated circuit stores a recordof the state of the mist generator device which is indicative of atleast one of the historic use of the mist generator device or the volumeof a liquid within the liquid chamber.

According to one aspect, there is provided a driver device for a mistinhaler device, the device comprising:

-   -   a battery;    -   an AC driver for converting a voltage from the battery into an        AC drive signal at a predetermined frequency to drive an        ultrasonic transducer;    -   an active power monitoring arrangement for monitoring the active        power used by the ultrasonic transducer when the ultrasonic        transducer is driven by the AC drive signal, wherein the active        power monitoring arrangement provides a monitoring signal which        is indicative of an active power used by the ultrasonic        transducer;    -   a processor for controlling the AC driver and for receiving the        monitoring signal drive from the active power monitoring        arrangement; and    -   a memory storing instructions which, when executed by the        processor, cause the processor to:    -   A. control the AC driver to output an AC drive signal to the        ultrasonic transducer at a predetermined sweep frequency;    -   B. calculate the active power being used by the ultrasonic        transducer based on the monitoring signal;    -   C. control the AC driver to modulate the AC drive signal to        maximise the active power being used by the ultrasonic        transducer;    -   D. store a record in the memory of the maximum active power used        by the ultrasonic transducer and the sweep frequency of the AC        drive signal;    -   E. repeat steps A-D for a predetermined number of iterations        with the sweep frequency incrementing with each iteration such        that, after the predetermined number of iterations has occurred,        the sweep frequency has been incremented from a start sweep        frequency to an end sweep frequency;    -   F. identify from the records stored in the memory the optimum        frequency for the AC drive signal which is the sweep frequency        of the AC drive signal at which a maximum active power is used        by the ultrasonic transducer; and    -   G. control the AC driver to output an AC drive signal to the        ultrasonic transducer at the optimum frequency to drive the        ultrasonic transducer to atomise a liquid.

In some examples, the active power monitoring arrangement comprises: acurrent sensing arrangement for sensing a drive current of the AC drivesignal driving the ultrasonic transducer, wherein the active powermonitoring arrangement provides a monitoring signal which is indicativeof the sensed drive current.

In some examples, the current sensing arrangement comprises: anAnalog-to-Digital Converter which converts the sensed drive current intoa digital signal for processing by the processor.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D with the sweepfrequency being incremented from a start sweep frequency of 2900 kHz toan end sweep frequency of 2960 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D with the sweepfrequency being incremented from a start sweep frequency of 2900 kHz toan end sweep frequency of 3100 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: in step G, control the AC driverto output an AC drive signal to the ultrasonic transducer at frequencywhich is shifted by a predetermined shift amount from the optimumfrequency.

In some examples, the predetermined shift amount is between 1-10% of theoptimum frequency.

In some examples, the battery is a 3.7V DC Li—Po battery.

In some examples, the driver device further comprises: a pressure sensorfor sensing a flow of air along a driver device flow path which extendsthrough the driver device.

In some examples, the driver device further comprises: a wirelesscommunication system which is in communication with the processor, thewireless communication system being configured to transmit and receivedata between the driver device and a computing device.

In some examples, the driver device further comprises: a driver devicehousing which is at least partly of metal, wherein the driver devicehousing houses the battery, the processor, the memory, the active powermonitoring arrangement and the AC driver, and wherein the driver devicehousing comprises a recess for receiving and retaining part of the mistgenerator device.

In some examples, the AC driver modulates the AC drive signal by pulsewidth modulation to maximise the active power being used by theultrasonic transducer.

It is noted that the expression “mist” used in the following disclosuremeans the liquid is not heated as usually in traditional inhalers knownfrom the prior art. In fact, traditional inhalers use heating elementsto heat the liquid above its boiling temperature to produce a vapour,which is different from a mist.

In fact, when sonicating liquids at high intensities, the sound wavesthat propagate into the liquid media result in alternating high-pressure(compression) and low-pressure (rarefaction) cycles, at different ratesdepending on the frequency. During the low-pressure cycle,high-intensity ultrasonic waves create small vacuum bubbles or voids inthe liquid. When the bubbles attain a volume at which they can no longerabsorb energy, they collapse violently during a high-pressure cycle.This phenomenon is termed cavitation. During the implosion, very highpressures are reached locally. At cavitation, broken capillary waves aregenerated, and tiny droplets break the surface tension of the liquid andare quickly released into the air, taking mist form.

The following will explain more precisely the cavitation phenomenon.

When the liquid is atomised by ultrasonic vibrations, micro waterbubbles are produced in the liquid.

The bubble production is a process of formation of cavities created bythe negative pressure generated by intense ultrasonic waves generated bythe means of ultrasonic vibrations.

High intensity ultrasonic sound waves leading to rapid growth ofcavities with relatively low and negligible reduction in cavity sizeduring the positive pressure cycle.

Ultrasound waves, like all sound waves, consist of cycles of compressionand expansion. When in contact with a liquid, Compression cycles exert apositive pressure on the liquid, pushing the molecules together.Expansion cycles exert a negative pressure, pulling the molecules awayfrom another.

Intense ultrasound waves create regions of positive pressure andnegative pressure. A cavity can form and grow during the episodes ofnegative pressure. When the cavity attains a critical size, the cavityimplodes.

The amount of negative pressure needed depends on the type and purity ofthe liquid. For truly pure liquids, tensile strengths are so great thatavailable ultrasound generators cannot produce enough negative pressureto make cavities. In pure water, for instance, more than 1,000atmospheres of negative pressure would be required, yet the mostpowerful ultrasound generators produce only about 50 atmospheres ofnegative pressure. The tensile strength of liquids is reduced by the gastrapped within the crevices of the liquid particles. The effect isanalogous to the reduction in strength that occurs from cracks in solidmaterials. When a crevice filled with gas is exposed to anegative-pressure cycle from a sound wave, the reduced pressure makesthe gas in the crevice expand until a small bubble is released intosolution.

However, a bubble irradiated with ultrasound continually absorbs energyfrom alternating compression and expansion cycles of the sound wave.These cause the bubbles to grow and contract, striking a dynamic balancebetween the void inside the bubble and the liquid outside. In somecases, ultrasonic waves will sustain a bubble that simply oscillates insize. In other cases, the average size of the bubble will increase.

Cavity growth depends on the intensity of sound. High-intensityultrasound can expand the cavity so rapidly during the negative-pressurecycle that the cavity never has a chance to shrink during thepositive-pressure cycle. In this process, cavities can grow rapidly inthe course of a single cycle of sound.

For low-intensity ultrasound the size of the cavity oscillates in phasewith the expansion and compression cycles. The surface of a cavityproduced by low-intensity ultrasound is slightly greater duringexpansion cycles than during compression cycles. Since the amount of gasthat diffuses in or out of the cavity depends on the surface area,diffusion into the cavity during expansion cycles will be slightlygreater than diffusion out during compression cycles. For each cycle ofsound, then, the cavity expands a little more than it shrinks. Over manycycles the cavities will grow slowly.

It has been noticed that the growing cavity can eventually reach acritical size where it will most efficiently absorb energy from theultrasound. The critical size depends on the frequency of the ultrasoundwave. Once a cavity has experienced a very rapid growth caused by highintensity ultrasound, it can no longer absorb energy as efficiently fromthe sound waves. Without this energy input the cavity can no longersustain itself. The liquid rushes in and the cavity implodes due to anon-linear response.

The energy released from the implosion causes the liquid to befragmented into microscopic particles which are dispersed into the airas mist.

The equation for description of the above non-linear response phenomenonmay be described by the “Rayleigh-Plesset” equation. This equation canbe derived from the “Navier-Stokes” equation used in fluid dynamics.

The inventors approach was to rewrite the “Rayleigh-Plesset” equation inwhich the bubble volume, V, is used as the dynamic parameter and wherethe physics describing the dissipation is identical to that used in themore classical form where the radius is the dynamic parameter.

The equation used derived as follows:

$\frac{❘{\frac{1}{c^{2}}\frac{\delta^{?}\phi}{\delta t^{2}}}❘}{\nabla^{2}\phi} \sim \left( \frac{R}{\lambda} \right)^{2} \ll 1$${\frac{1}{4\pi}\left( \frac{4\pi}{3V} \right)^{\frac{1}{3}}\left( {\overset{¨}{V} - \frac{{\overset{.}{V}}^{2}(t)}{6V}} \right)} = {\frac{1}{\rho_{0}}\left( {{\left( {p_{0} + {2{\sigma\left( \frac{4\pi}{3V_{0}} \right)}^{\frac{1}{3}}} - p_{V}} \right)\left( \frac{V_{0}}{V} \right)^{\kappa}} + p_{V} - {2{\sigma\left( \frac{4\pi}{3V} \right)}^{\frac{1}{3}}} - {p_{0^{-}}{P(t)}}} \right)}$

wherein:V is the bubble volumeV₀ is the equilibrium bubble volumeρ₀ is the liquid density (assumed to be constant)σ is the surface tensionp_(v) is the vapour pressurep₀ is the static pressure in the liquid just outside the bubble wallκ is the polytropic index of the gast is the timeR(t) is the bubble radiusP(t) is the applied pressurec is the speed sound of the liquidϕ is the velocity potentialλ is the wavelength of the insonifying field

In the ultrasonic mist inhaler, the liquid has a liquid viscositybetween 1.05 Pa·sec and 1.412 Pa·sec.

By solving the above equation with the right parameters of viscosity,density and having a desired target bubble volume of liquid spray intothe air, it has been found that the frequency range of 2.8 MHz to 3.2MHz for liquid viscosity range of 1.05 Pa·s and 1.412 Pa·s produce abubble volume of about 0.25 to 0.5 microns.

The process of ultrasonic cavitation has a significant impact on thenicotine concentration in the produced mist.

No heating elements are involved, thereby leading to no burnt elementsand reducing second-hand smoke effects.

In some examples, said liquid comprises 57-70% (w/w) vegetable glycerineand 30-43% (w/w) propylene glycol, said propylene glycol includingnicotine and optionally flavourings.

In the ultrasonic mist inhaler, a capillary element may extend betweenthe sonication chamber and the liquid chamber.

In the ultrasonic mist inhaler, the capillary element is a material atleast partly in bamboo fibres.

The capillary element allows a high absorption capacity, a high rate ofabsorption as well as a high fluid-retention ratio.

It was found that the inherent properties of the proposed material usedfor the capillarity have a significant impact on the efficientfunctioning of the ultrasonic mist inhaler.

Further, inherent properties of the proposed material include a goodhygroscopicity while maintaining a good permeability. This allows thedrawn liquid to efficiently permeate the capillary while the observedhigh absorption capacity allows the retention of a considerable amountof liquid thus allowing the ultrasonic mist inhaler to last for a longertime when compared with the other products available in the market.

Another significant advantage of using the bamboo fibres is thenaturally occurring antimicrobial bio-agent namely “Kun” inherentlypresent within the bamboo fibre making it antibacterial, anti-fungal andodour resistant, making it suitable for medical applications. Theinherent properties have been verified using numerical analysisregarding the benefits of the bamboo fibre for sonication.

The following formulae have been tested with bamboo fibres material andothers material such cotton, paper, or other fibre strands for the useas capillary element and demonstrates that bamboo fibres have muchbetter properties for the use in sonication:

$C = {A + \frac{T}{W_{f}} - \frac{1}{P_{f}} + {\left( {1 - \alpha} \right)\frac{V_{d}}{W_{f}}}}$

wherein:C (cc/gm of fluid/gm) is the volume per mass of the liquid absorbeddivided by the dry mass of the capillary element,A (cm²) is the total surface area of the capillary elementT (cm) is the thickness of the capillary element,W_(f) (gm) is the mass of the dry capillary element,P_(f) (cc/g. sec) is the density of the dry capillary element,α is the ratio of increase in volume of capillary element upon wettingto the volume of liquid diffused in the capillary element,V_(d) (cc) is the amount of liquid diffused in the capillary element,

${{Absorbent}{Rate}},{Q = {\frac{\pi r{\gamma 1}\cos\theta}{2\eta} \cdot \left( {\frac{T}{W_{f}} - \frac{1}{AP_{f}}} \right)}}$

Q (cc/sec) is the amount of liquid absorbed per unit time,r (cm) is the radius of the pores within the capillary element,γ (N/m) is the surface tension of the liquid,θ (degrees) is the angle of contact of the fibre,η (m²/sec) is the viscosity of the fluid.

In the ultrasonic mist inhaler, the capillary element may be a materialat least partly in bamboo fibres.

In the ultrasonic mist inhaler, the capillary element material may be100% bamboo fibre.

Extensive testing has concluded that a 100% pure bamboo fibre is themost optimal choice for sonication.

In the ultrasonic mist inhaler, the capillary element material may be atleast 75% bamboo fibre and, optionally, 25% cotton.

Capillary element from 100% pure bamboo fibre or with a high percentageof bamboo fibres demonstrates a high absorption capacity as well asimproved fluid transmission making it an optimal choice for theapplication of the ultrasonic mist inhaler.

In the ultrasonic mist inhaler, the capillary element may have a flatshape.

In the ultrasonic mist inhaler, the capillary element may comprise acentral portion and a peripheral portion.

In the ultrasonic mist inhaler, the peripheral portion may have anL-shape cross section extending down to the liquid chamber.

In the ultrasonic mist inhaler, the central portion may have a U-shapecross section extending down to the sonication chamber.

The ultrasonic mist inhaler according to one example, wherein saidliquid to be received in the liquid chamber comprises 57-70% (w/w)vegetable glycerin and 30-43% (w/w) propylene glycol, said propyleneglycol including nicotine and flavourings.

An ultrasonic mist inhaler or a personal ultrasonic atomiser device,comprising:

-   -   a liquid reservoir structure comprising a liquid chamber or        cartridge adapted to receive liquid to be atomised,    -   a sonication chamber in fluid communication with the liquid        chamber or cartridge, wherein said liquid to be received in the        liquid chamber comprises 57-70% (w/w) vegetable glycerin and        30-43% (w/w) propylene glycol, said propylene glycol including        nicotine and flavourings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the present invention may be more readily understood,embodiments of the present invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is an exploded view of components of an ultrasonic mist inhaler.

FIG. 2 is an exploded view of components of an inhaler liquid reservoirstructure.

FIG. 3 is a cross section view of components of an inhaler liquidreservoir structure.

FIG. 4A is an isometric view of an airflow member of the inhaler liquidreservoir structure according to FIGS. 2 and 3 .

FIG. 4B is a cross section view of the airflow member shown in FIG. 4A.

FIG. 5 is schematic diagram showing a piezoelectric transducer modelledas an RLC circuit.

FIG. 6 is graph of frequency versus log impedance of an RLC circuit.

FIG. 7 is graph of frequency versus log impedance showing inductive andcapacitive regions of operation of a piezoelectric transducer.

FIG. 8 is flow diagram showing the operation of a frequency controller.

FIG. 9 is a diagrammatic perspective view of a mist inhaler device ofthis disclosure.

FIG. 10 is a diagrammatic perspective view of a mist inhaler device ofthis disclosure.

FIG. 11 is a diagrammatic perspective view of a mist generator device ofthis disclosure.

FIG. 12 is a diagrammatic perspective view of a mist generator device ofthis disclosure.

FIG. 13 is a diagrammatic exploded perspective view of a mist generatordevice of this disclosure.

FIG. 14 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 15 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 16 is a diagrammatic perspective view of a capillary element ofthis disclosure.

FIG. 17 is a diagrammatic perspective view of a capillary element ofthis disclosure.

FIG. 18 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 19 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 20 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 21 is a diagrammatic perspective view of an absorbent element ofthis disclosure.

FIG. 22 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 23 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 24 is a diagrammatic perspective view of an absorbent element ofthis disclosure.

FIG. 25 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 26 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 27 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 28 is a diagrammatic perspective view of a circuit board of thisdisclosure.

FIG. 29 is a diagrammatic perspective view of a circuit board of thisdisclosure.

FIG. 30 is a diagrammatic exploded perspective view of a mist generatordevice of this disclosure.

FIG. 31 is a diagrammatic exploded perspective view of a mist generatordevice of this disclosure.

FIG. 32 is a cross sectional view of a mist generator device of thisdisclosure.

FIG. 33 is a cross sectional view of a mist generator device of thisdisclosure.

FIG. 34 is a cross sectional view of a mist generator device of thisdisclosure.

FIG. 35 is a diagrammatic exploded perspective view of a driver deviceof this disclosure.

FIG. 36 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 37 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 38 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 39 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 40 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 41 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 42 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 43 is a diagrammatic perspective view of an end cap of a driverdevice of this disclosure.

FIG. 44 is a diagrammatic perspective view of the housing of a driverdevice of this disclosure.

FIG. 45 is a graph showing the result of an EMC test for a mist inhalerdevice of this disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, concentrations, applicationsand arrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, the attachment of a first feature and a secondfeature in the description that follows may include embodiments in whichthe first feature and the second feature are attached in direct contact,and may also include embodiments in which additional features may bepositioned between the first feature and the second feature, such thatthe first feature and the second feature may not be in direct contact.In addition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

The following disclosure describes representative examples. Each examplemay be considered to be an embodiment and any reference to an “example”may be changed to “embodiment” in the present disclosure.

Some parts of the present disclosure are directed to an electronicvaporising inhaler. However, other examples are envisioned, such as aninhaler for hookah, flavoured liquids, medicine, and herbal supplements.Additionally, the device can be packaged to look like an object otherthan a cigarette. For instance, the device could resemble anothersmoking instrument, such as a pipe, water pipe, or slide, or the devicecould resemble another non-smoking related object.

Ultrasonic mist inhalers are either disposable or reusable. The term“reusable” as used herein implies that the energy storage device isrechargeable or replaceable or that the liquid is able to be replenishedeither through refilling or through replacement of the liquid reservoirstructure. Alternatively, in some examples reusable electronic device isboth rechargeable and the liquid can be replenished.

Conventional electronic vaporising inhaler tend to rely on inducing hightemperatures of a metal component configured to heat a liquid in theinhaler, thus vaporising the liquid that can be breathed in. The liquidtypically contains nicotine and flavourings blended into a solution ofpropylene glycol (PG) and vegetable glycerin (VG), which is vaporisedvia a heating component at high temperatures. Problems with conventionalinhaler may include the possibility of burning metal and subsequentbreathing in of the metal along with the burnt liquid. In addition, somemay not prefer the burnt smell or taste caused by the heated liquid.

FIG. 1 to FIG. 4 illustrates an example of an ultrasonic inhalercomprising a sonication chamber.

FIG. 1 depicts a disposable ultrasonic mist inhaler 100. As can be seenin FIG. 1 , the ultrasonic mist inhaler 100 has a cylindrical body witha relatively long length as compared to the diameter. In terms of shapeand appearance, the ultrasonic mist inhaler 100 is designed to mimic thelook of a typical cigarette. For instance, the inhaler can feature afirst portion 101 that primarily simulates the tobacco rod portion of acigarette and a second portion 102 that primarily simulates a filter. Inthe disposable example, the first portion and second portion are regionsof a single, but-separable device. The designation of a first portion101 and a second portion 102 is used to conveniently differentiate thecomponents that are primarily contained in each portion.

As can be seen in FIG. 1 , the ultrasonic mist inhaler comprises amouthpiece 1, a liquid reservoir structure 2 and a casing 3. The firstportion 101 comprises the casing 3 and the second portion 102 comprisesthe mouthpiece 1 and the reservoir structure 2.

The first portion 101 contains the power supply energy.

An electrical storage device 30 powers the ultrasonic mist inhaler 100.The electrical storage device 30 can be a battery, including but notlimited to a lithium-ion, alkaline, zinc-carbon, nickel-metal hydride,or nickel-cadmium battery; a super capacitor; or a combination thereof.In the disposable example, the electrical storage device 30 is notrechargeable, but, in the reusable example, the electrical storagedevice 30 would be selected for its ability to recharge. In thedisposable example, the electrical storage device is primarily selectedto deliver a constant voltage over the life of the inhaler 100.Otherwise, the performance of the inhaler would degrade over time.Preferred electrical storage devices that are able to provide aconsistent voltage output over the life of the device includelithium-ion and lithium polymer batteries.

The electrical storage device 30 has a first end 30 a that generallycorresponds to a positive terminal and a second end 30 b that generallycorresponds to a negative terminal. The negative terminal is extendingto the first end 30 a.

Because the electrical storage device 30 is located in the first portion101 and the liquid reservoir structure 2 is located in the secondportion 102, the joint needs to provide electrical communication betweenthose components. In the present invention, electrical communication isestablished using at least an electrode or probe that is compressedtogether when the first portion 101 is tightened into the second portion102.

In order for this example to be reusable, the electrical storage device30 is rechargeable. The casing 3 contains a charging port 32.

The integrated circuit 4 has a proximal end 4 a and a distal end 4 b.The positive terminal at the first end 30 a of the electrical storagedevice 30 is in electrical communication with a positive lead of theflexible integrated circuit 4. The negative terminal at the second end30 b of the electrical storage device 30 is in electrical communicationwith a negative lead of the integrated circuit 4. The distal end 4 b ofthe integrated circuit 4 comprises a microprocessor. The microprocessoris configured to process data from a sensor, to control a light, todirect current flow to means of ultrasonic vibrations 5 in the secondportion 102, and to terminate current flow after a pre-programmed amountof time.

The sensor detects when the ultrasonic mist inhaler 100 is in use (whenthe user draws on the inhaler) and activates the microprocessor. Thesensor can be selected to detect changes in pressure, air flow, orvibration. In one example, the sensor is a pressure sensor. In thedigital device, the sensor takes continuous readings which in turnrequires the digital sensor to continuously draw current, but the amountis small and overall battery life would be negligibly affected.

In some examples, the integrated circuit 4 comprises a H bridge, whichmay be formed by 4 MOSFETs to convert a direct current into an alternatecurrent at high frequency. Referring to FIG. 2 and FIG. 3 ,illustrations of a liquid reservoir structure 2 according to an exampleare shown. The liquid reservoir structure 2 comprises a liquid chamber21 adapted to receive liquid to be atomised and a sonication chamber 22in fluid communication with the liquid chamber 21.

In the example shown, the liquid reservoir structure 2 comprises aninhalation channel 20 providing an air passage from the sonicationchamber 22 toward the surroundings.

As an example of sensor position, the sensor may be located in thesonication chamber 22.

The inhalation channel 20 has a frustoconical element 20 a and an innercontainer 20 b.

As depicted in FIGS. 4A and 48 , further the inhalation channel 20 hasan airflow member 27 for providing air flow from the surroundings to thesonication chamber 22.

The airflow member 27 has an airflow bridge 27 a and an airflow duct 27b made in one piece, the airflow bridge 27 a having two airway openings27 a′ forming a portion of the inhalation channel 20 and the airflowduct 27 b extending in the sonication chamber 22 from the airflow bridge27 a for providing the air flow from the surroundings to the sonicationchamber.

The airflow bridge 27 a cooperates with the frustoconical element 20 aat the second diameter 20 a 2.

The airflow bridge 27 a has two opposite peripheral openings 27 a″providing air flow to the airflow duct 27 b.

The cooperation with the airflow bridge 27 a and the frustoconicalelement 20 a is arranged so that the two opposite peripheral openings 27a″ cooperate with complementary openings 20 a″ in the frustoconicalelement 20 a.

The mouthpiece 1 and the frustoconical element 20 a are radially spacedand an airflow chamber 28 is arranged between them.

As depicted in FIGS. 1 and 2 , the mouthpiece 1 has two oppositeperipheral openings 1″.

The peripheral openings 27 a″, 20 a″, 1″ of the airflow bridge 27 a, thefrustoconical element 20 a and the mouthpiece 1 directly supply maximumair flow to the sonication chamber 22.

The frustoconical element 20 a includes an internal passage, aligned inthe similar direction as the inhalation channel 20, having a firstdiameter 20 a 1 less than that of a second diameter 20 a 2, such thatthe internal passage reduces in diameter over the frustoconical element20 a.

The frustoconical element 20 a is positioned in alignment with the meansof ultrasonic vibrations 5 and a capillary element 7, wherein the firstdiameter 20 a 1 is linked to an inner duct 11 of the mouthpiece 1 andthe second diameter 20 a 2 is linked to the inner container 20 b.

The inner container 20 b has an inner wall delimiting the sonicationchamber 22 and the liquid chamber 21.

The liquid reservoir structure 2 has an outer container 20 c delimitingthe outer wall of the liquid chamber 21.

The inner container 20 b and the outer container 20 c are respectivelythe inner wall and the outer wall of the liquid chamber 21.

The liquid reservoir structure 2 is arranged between the mouthpiece 1and the casing 3 and is detachable from the mouthpiece 1 and the casing3.

The liquid reservoir structure 2 and the mouthpiece 1 or the casing 3may include complimentary arrangements for engaging with one another;further such complimentary arrangements may include one of thefollowing: a bayonet type arrangement; a threaded engaged typearrangement; a magnetic arrangement; or a friction fit arrangement;wherein the liquid reservoir structure 2 includes a portion of thearrangement and the mouthpiece 1 or the casing 3 includes thecomplimentary portion of the arrangement.

In the reusable example, the components are substantially the same. Thedifferences in the reusable example vis-a-vis the disposable example arethe accommodations made to replace the liquid reservoir structure 2.

As shown in FIG. 3 , the liquid chamber 21 has a top wall 23 and abottom wall 25 closing the inner container 20 b and the outer container20 c of the liquid chamber 21.

The capillary element 7 is arranged between a first section 20 b 1 and asecond section 20 b 2 of the inner container 20 b.

The capillary element 7 has a flat shape extending from the sonicationchamber to the liquid chamber.

As depicted in FIG. 2 or 3 , the capillary element 7 comprises a centralportion 7 a in U-shape and a peripheral portion 7 b in L-shape.

The L-shape portion 7 b extends into the liquid chamber 21 on the innercontainer 20 b and along the bottom wall 25.

The U-shape portion 7 a is contained into the sonication chamber 21. TheU-shape portion 7 a on the inner container 20 b and along the bottomwall 25.

In the ultrasonic mist inhaler, the U-shape portion 7 a has an innerportion 7 a 1 and an outer portion 7 a 2, the inner portion 7 a 1 beingin surface contact with an atomisation surface 50 of the means ofultrasonic vibrations 5 and the outer portion 7 a 2 being not in surfacecontact with the means of ultrasonic vibrations 5.

The bottom wall 25 of the liquid chamber 21 is a bottom plate 25 closingthe liquid chamber 21 and the sonication chamber 22. The bottom plate 25is sealed, thus preventing leakage of liquid from the sonication chamber22 to the casing 3.

The bottom plate 25 has an upper surface 25 a having a recess 25 b onwhich is inserted an elastic member 8. The means of ultrasonicvibrations 5 are supported by the elastic member 8. The elastic member 8is formed from an annular plate-shaped rubber having an inner hole 8′wherein a groove is designed for maintaining the means of ultrasonicvibrations 5.

The top wall 23 of the liquid chamber 21 is a cap 23 closing the liquidchamber 23.

The top wall 23 has a top surface 23 representing the maximum level ofthe liquid that the liquid chamber 21 may contain and the bottom surface25 representing the minimum level of the liquid in the liquid chamber21.

The top wall 23 is sealed, thus preventing leakage of liquid from theliquid chamber 21 to the mouthpiece 1.

The top wall 23 and the bottom wall 25 are fixed to the liquid reservoirstructure 2 by means of fixation such as screws, glue or friction.

As depicted in FIG. 3 , the elastic member is in line contact with themeans of ultrasonic vibrations 5 and prevents contact between the meansof ultrasonic vibrations 5 and the inhaler walls, suppression ofvibrations of the liquid reservoir structure are more effectivelyprevented. Thus, fine particles of the liquid atomised by the atomisingmember can be sprayed farther.

As depicted in FIG. 3 , the inner container 20 b has openings 20 b′between the first section 20 b 1 and the second section 20 b 2 fromwhich the capillary element 7 is extending from the sonication chamber21. The capillary element 7 absorbs liquid from the liquid chamber 21through the apertures 20 b′. The capillary element 7 is a wick. Thecapillary element 7 transports liquid to the sonication chamber 22 viacapillary action. In some examples, the capillary element 7 is made ofbamboo fibres. In some examples, the capillary element 7 may be of athickness between 0.27 mm and 0.32 mm and have a density between 38 g/m²and 48 g/m².

As can be seen in FIG. 3 , the means of ultrasonic vibrations 5 aredisposed directly below the capillary element 7.

The means of ultrasonic vibrations 5 may be a transducer. For example,the means of ultrasonic vibrations 5 may be a piezoelectric transducer,which may be designed in a circular plate-shape. The material of thepiezoelectric transducer may be ceramic.

A variety of transducer materials can also be used for the means ofultrasonic vibrations 5.

The end of the airflow duct 27 b 1 faces the means of ultrasonicvibrations 5. The means of ultrasonic vibrations 5 are in electricalcommunication with electrical contactors 101 a, 101 b. It is noted that,the distal end 4 b of the integrated circuit 4 has an inner electrodeand an outer electrode. The inner electrode contacts the firstelectrical contact 101 a which is a spring contact probe, and the outerelectrode contacts the second electrical contact 101 b which is a sidepin. Via the integrated circuit 4, the first electrical contact 101 a isin electrical communication with the positive terminal of the electricalstorage device 30 by way of the microprocessor, while the secondelectrical contact 101 b is in electrical communication with thenegative terminal of the electrical storage device 30.

The electrical contacts 101 a, 101 b crossed the bottom plate 25. Thebottom plate 25 is designed to be received inside the perimeter wall 26of the liquid reservoir structure 2.

The bottom plate 25 rests on complementary ridges, thereby creating theliquid chamber 21 and sonication chamber 22.

The inner container 20 b comprises a circular inner slot 20 d on which amechanical spring is applied.

By pushing the central portion 7 a 1 onto the means of ultrasonicvibrations 5, the mechanical spring 9 ensures a contact surface betweenthem.

The liquid reservoir structure 2 and the bottom plate 25 can be madeusing a variety of thermoplastic materials.

When the user draws on the ultrasonic mist inhaler 100, an air flow isdrawn from the peripheral openings 1″ and penetrates the airflow chamber28, passes the peripheral openings 27 a″ of the airflow bridge 27 a andthe frustoconical element 20 a and flows down into the sonicationchamber 22 via the airflow duct 27 b directly onto the capillary element7. At the same time, the liquid is drawn from the reservoir chamber 21by capillarity, through the plurality of apertures 20 b′, and into thecapillary element 7. The capillary element 7 brings the liquid intocontact with the means of ultrasonic vibrations 5 of the inhaler 100.The user's draw also causes the pressure sensor to activate theintegrated circuit 4, which directs current to the means of ultrasonicvibrations 5. Thus, when the user draws on the mouthpiece 1 of theinhaler 100, two actions happen at the same time. Firstly, the sensoractivates the integrated circuit 4, which triggers the means ofultrasonic vibrations 5 to begin vibrating. Secondly, the draw reducesthe pressure outside the reservoir chamber 21 such that flow of theliquid through the apertures 20 b′ begins, which saturates the capillaryelement 7. The capillary element 7 transports the liquid to the means ofultrasonic vibrations 5, which causes bubbles to form in a capillarychannel by the means of ultrasonic vibrations 5 and mist the liquid.Then, the mist liquid is drawn by the user.

In some examples, the integrated circuit 4 comprises a frequencycontroller which is configured to control the frequency at which themeans of ultrasonic vibrations 5 operates. The frequency controllercomprises a processor and a memory, the memory storing executableinstructions which, when executed by the processor, cause the processorto perform at least one function of the frequency controller.

As described above, in some examples the ultrasonic mist inhaler 100drives the means of ultrasonic vibrations 5 with a signal having afrequency of 2.8 MHz to 3.2 MHz in order to vaporise a liquid having aliquid viscosity of 1.05 Pa·s to 1.412 Pa·s in order to produce a bubblevolume of about 0.25 to 0.5 microns. However, for liquids with adifferent viscosity or for other applications it the means of ultrasonicvibrations 5 may be driven at a different frequency.

For each different application for a mist generation system, there is anoptimum frequency or frequency range for driving the means of ultrasonicvibrations 5 in order to optimize the generation of mist. In exampleswhere the means of ultrasonic vibrations 5 is a piezoelectrictransducer, the optimum frequency or frequency range will depend on atleast the following four parameters:

1. Transducer Manufacturing Processes

In some examples, the means of ultrasonic vibrations 5 comprises apiezoelectric ceramic. The piezoelectric ceramic is manufactured bymixing compounds to make a ceramic dough and this mixing process may notbe consistent throughout production.

This inconsistency can give rise to a range of different resonantfrequencies of the cured piezoelectric ceramic.

If the resonant frequency of the piezoelectric ceramic does notcorrespond to the required frequency of operation of the device then nomist is produced during the operation of the device. In the case of anicotine mist inhaler, even a slight offset in the resonant frequency ofthe piezoelectric ceramic is enough to impact the production of mist,meaning that the device will not deliver adequate nicotine levels to theuser.

2. Load on Transducer

During operation, any changes in the load on the piezoelectrictransducer will inhibit the overall displacement of the oscillation ofthe piezoelectric transducer. To achieve optimal displacement of theoscillation of the piezoelectric transducer, the drive frequency must beadjusted to enable the circuit to provide adequate power for maximumdisplacement.

The types of loads that can affect the oscillator's efficiency caninclude the amount of liquid on the transducer (dampness of the wickingmaterial), and the spring force applied to the wicking material to keeppermanent contact with the transducer. It may also include the means ofelectrical connection.

3. Temperature

Ultrasonic oscillations of the piezoelectric transducer are partiallydamped by its assembly in a device. This may include the transducerbeing placed in a silicone/rubber ring, and the spring exerting pressureonto the wicking material that is above the transducer. This dampeningof the oscillations causes rise in local temperatures on and around thetransducer.

An increase in temperature affects the oscillation due to changes in themolecular behaviour of the transducer. An increase in the temperaturemeans more energy to the molecules of the ceramic, which temporarilyaffects its crystalline structure. Although the effect is reversed asthe temperature reduces, a modulation in supplied frequency is requiredto maintain optimal oscillation. This modulation of frequency cannot beachieved with a conventional fixed frequency device.

An increase in temperature also reduces the viscosity of the solution(e-liquid) which is being vaporized, which may require an alteration tothe drive frequency to induce cavitation and maintain continuous mistproduction. In the case of a conventional fixed frequency device, areduction in the viscosity of the liquid without any change in the drivefrequency will reduce or completely stop mist production, rendering thedevice inoperable.

4. Distance to Power Source

The oscillation frequency of the electronic circuit can change dependingon the wire-lengths between the transducer and the oscillator-driver.The frequency of the electronic circuit is inversely proportional to thedistance between the transducer and the remaining circuit.

Although the distance parameter is primarily fixed in a device, it canvary during the manufacturing process of the device, reducing theoverall efficiency of the device.

Therefore, it is desirable to modify the drive frequency of the deviceto compensate for the variations and optimise the efficiency of thedevice.

A piezoelectric transducer can be modelled as an RLC circuit in anelectronic circuit, as shown in FIG. 5 . The four parameters describedabove may be modelled as alterations to the overall inductance,capacitance, and/or resistance of the RLC circuit, changing theresonance frequency range supplied to the transducer. As the frequencyof the circuit increases to around the resonance point of thetransducer, the log Impedance of the overall circuit dips to a minimumand then rises to a maximum before settling to a median range.

FIG. 6 shows a generic graph explaining the change in overall impedancewith increase in frequency in an RLC circuit. FIG. 7 shows how apiezoelectric transducer acts as a capacitor in a first capacitiveregion at frequencies below a first predetermined frequency f_(s) and ina second capacitive region at frequencies above a second predeterminedfrequency f_(p). The piezoelectric transducer acts as an inductor in aninductive region at frequencies between the first and secondpredetermined frequencies f_(s), f_(p). In order to maintain optimaloscillation of the transducer and hence maximum efficiency, the currentflowing through the transducer must be maintained at a frequency withinthe inductive region.

The frequency controller of the device of some examples is configured tomaintain the frequency of oscillation of the piezoelectric transducer(the means of ultrasonic vibrations 5) within the inductive region, inorder to maximise the efficiency of the device.

The frequency controller is configured to perform a sweep operation inwhich the frequency controller drives the transducer at frequencieswhich track progressively across a predetermined sweep frequency range.As the frequency controller performs the sweep, the frequency controllermonitors an Analog-to-Digital Conversion (ADC) value of anAnalog-to-Digital converter which is coupled to the transducer. In someexamples the ADC value is a parameter of the ADC which is proportionalto the voltage across the transducer. In other examples, the ADC valueis a parameter of the ADC which is proportional to the current flowingthrough the transducer.

As will be described in more detail below, the frequency controller ofsome examples determines the active power being used by the ultrasonictransducer by monitoring the current flowing through the transducer.

During the sweep operation, the frequency controller locates theinductive region of the frequency for the transducer. Once the frequencycontroller has identified the inductive region, the frequency controllerrecords the ADC value and locks the drive frequency of the transducer ata frequency within the inductive region (i.e. between the first andsecond predetermined frequencies f_(s), f_(p)) in order to optimise theultrasonic cavitation by the transducer. When the drive frequency islocked within the inductive region, the electro-mechanical couplingfactor of the transducer is maximised, thereby maximising the efficiencyof the device.

In some examples, the frequency controller is configured to perform thesweep operation to locate the inductive region each time the oscillationis started or re-started. In the examples, the frequency controller isconfigured to lock the drive frequency at a new frequency within theinductive region each time the oscillation is started and therebycompensate for any changes in the parameters that affect the efficiencyof operation of the device.

In some examples, the frequency controller ensures optimal mistproduction and maximises efficiency of medication delivery to the user.In some examples, the frequency controller optimises the device andimproves the efficiency and maximises nicotine delivery to the user.

In other examples, the frequency controller optimises the device andimproves the efficiency of any other device which uses ultrasound. Insome examples, the frequency controller is configured for use withultrasound technology for therapeutic applications in order to extendthe enhancement of drug release from an ultrasound-responsive drugdelivery system. Having precise, optimal frequency during operation,ensures that the microbubbles, nanobubbles, nanodroplets, liposome,emulsions, micelles or any other delivery systems are highly effective.

In some examples, in order to ensure optimal mist generation and optimaldelivery of compounds as described above, the frequency controller isconfigured to operate in a recursive mode. When the frequency controlleroperates in the recursive mode, the frequency controller runs the sweepof frequencies periodically during the operation of the device andmonitors the ADC value to determine if the ADC value is above apredetermined threshold which is indicative of optimal oscillation ofthe transducer.

In some examples, the frequency controller runs the sweep operationwhile the device is in the process of aerosolising liquid in case thefrequency controller is able to identify a possible better frequency forthe transducer. If the frequency controller identifies a betterfrequency, the frequency controller locks the drive frequency at thenewly identified better frequency in order to maintain optimal operationof the device.

In some examples, the frequency controller runs the sweep of frequenciesfor a predetermined duration periodically during the operation of thedevice. In the case of the device of the examples described above, thepredetermined duration of the sweep and the time period between sweepsare selected to optimise the functionality of the device. Whenimplemented in an ultrasonic mist inhaler device, this will ensure anoptimum delivery to a user throughout the user's inhalation.

FIG. 8 shows a flow diagram of the operation of the frequency controllerof some examples.

The following disclosure discloses further examples of mist inhalerdevices which comprise many of the same elements as the examplesdescribed above. Elements of the examples described above may beinterchanged with any of the elements of the examples described in theremaining part of this disclosure.

To ensure adequate aerosol production, in this example the mist inhalerdevice comprises an ultrasonic/piezoelectric transducer of exactly orsubstantially 16 mm diameter. This transducer is manufactured tospecific capacitance and impedance values to control the frequency andpower required for desired aerosol volume production.

A horizontally placed disc-shaped 16 mm diameter ultrasonic transducerwould result in a large device that may not be ergonomic as handheld. Tomitigate this concern, the ultrasonic transducer of this example is heldvertically in the sonication chamber (the planar surface of theultrasonic transducer is generally parallel with the flow of aerosolmist to the mouthpiece and/or generally parallel to the longitudinallength of the mist inhaler device). Put another way, the ultrasonictransducer is generally perpendicular to a base of the mist inhalerdevice.

Referring now to FIGS. 9 and 10 of the accompanying drawings, a mistinhaler device 200 of some examples comprises a mist generator device201 and a driver device 202. The driver device 202 is, in this example,provided with a recess 203 which receives and retains part of the mistgenerator device 201. The mist generator 201 can therefore be coupledwith the driver device 202 to form a compact and portable mist inhalerdevice 200, as shown in FIG. 9 .

Referring now to FIGS. 11 to 13 of the accompanying drawings, the mistgenerator device 201 comprises a mist generator housing 204 which iselongate and optionally formed from two housing portions 205, 206 whichare attached to one another. The mist generator housing 204 comprises anair inlet port 207 and a mist outlet port 208.

In this example, the mist generator housing 204 is of injection mouldedplastic, specifically polypropylene that is typically used for medicalapplications. In this example, the mist generator housing 204 is of aheterophasic copolymer. More particularly a BF970MO heterophasiccopolymer, which has an optimum combination of very high stiffness andhigh impact strength. The mist generator housing parts moulded with thismaterial exhibit good anti-static performance.

A heterophasic copolymer such as polypropylene is particularly suitablefor the mist generator housing 204 since this material does not causecondensation of the aerosol as it flows from the sonication chamber 219through the mouthpiece to the user. This plastic material can also bedirectly recycled easily using industrial shredding and cleaningprocesses.

In FIGS. 9, 10 and 12 , the mist outlet port 208 is closed by a closureelement 209. However, it is to be appreciated that when the mist inhalerdevice 200 is in use, the closure element 209 is removed from the mistoutlet port 208, as shown in FIG. 11 .

Referring now to FIGS. 14 and 15 , the mist generator device 200comprises a transducer holder 210 which is held within the mistgenerator housing 204. The transducer holder 210 comprises a bodyportion 211 which, in this example, is cylindrical or generallycylindrical in shape with circular upper and lower openings 212, 213.The transducer holder 210 is provided with an internal recess 214 forreceiving an edge of an ultrasonic transducer 215, as shown in FIG. 15 .

The transducer holder 210 incorporates a cutaway section 216 throughwhich an electrode 217 extends from the ultrasonic transducer 215 sothat the electrode 217 may be connected electrically to an AC driver ofthe drive device, as described in more detail below.

Referring again to FIG. 13 , the mist generator device 201 comprises aliquid chamber 218 which is provided within the mist generator housing204. The liquid chamber 218 is for containing a liquid to be atomised.In some examples, a liquid is contained in the liquid chamber 218. Inother examples, the liquid chamber 218 is empty initially and the liquidchamber is filled with a liquid subsequently.

A liquid (also referred to herein as an e-liquid) composition suitablefor use in an ultrasonic device that is powered at a frequency of 3.0MHz (±0.2 MHz) by a 3.7V lithium polymer (LiPo) battery consisting of anicotine salt consisting of nicotine levulinate wherein:

The relative amount of vegetable glycerin in the composition is: from 55to 80% (w/w), or from 60 to 80% (w/w), or from 65 to 75% (w/w), or 70%(w/w); and/or,

The relative amount of propylene glycol in the composition is: from 5 to30% (w/w), or from 10 to 30% (w/w), or from 15 to 25% (w/w), or 20%(w/w); and/or,

The relative amount of water in the composition is: from 5 to 15% (w/w),or from 7 to 12% (w/w), or 10% (w/w); and/or,

The amount of nicotine and/or nicotine salt in the composition is: from0.1 to 80 mg/ml, or from 0.1 to 50 mg/ml, or from 1 to 25 mg/ml, or from10 to 20 mg/ml, or 17 mg/ml.

In some examples, the mist generator device 201 contains an e-liquidhaving a liquid viscosity between 1.05 Pa·s and 1.412 Pa·s.

In some examples, the liquid chamber 218 contains a liquid comprising anicotine levulinate salt at a 1:1 molar ratio.

In some examples, the liquid chamber 218 contains a liquid having aliquid viscosity between 1.05 Pa·s and 1.412 Pa·s and a liquid densitybetween 1.1 g/ml and 1.3 g/ml.

By using an e-liquid with the correct parameters of viscosity, densityand having a desired target bubble volume of liquid spray into the air,it has been found that the frequency range of 2.8 MHz to 3.2 MHz forliquid viscosity range of 1.05 Pa·s and 1.412 Pa·s and density ofapproximately 1.1-1.3 g/mL (get density ranges from Hertz) produce adroplet volume where 90% of droplets are below 1 micron and 50% of thoseare less than 0.5 microns.

The mist generator device 201 comprises a sonication chamber 219 whichis provided within the mist generator housing 204.

Returning to FIGS. 14 and 15 , the transducer holder 210 comprises adivider portion 220 which provides a barrier between the liquid chamber218 and the sonication chamber 219. The barrier provided by the dividerportion 220 minimises the risk of the sonication chamber 219 being isflooded with liquid from the liquid chamber 218 or for a capillaryelement over the ultrasonic transducer 215 becoming oversaturated,either of which would overload and reduce the efficiency of theultrasonic transducer 215. Moreover, flooding the sonication chamber 219or over saturating the capillary element could also cause an unpleasantexperience with the liquid being sucked in by the user duringinhalation. To mitigate this risk, the divider portion 220 of thetransducer holder 210 sits as a wall between the sonication chamber 219and the liquid chamber 218.

The divider portion 220 comprises a capillary aperture 221 which is theonly means by which liquid can flow from the liquid chamber 218 to thesonication chamber 219, via a capillary element. In this example, thecapillary aperture 221 is an elongate slot having a width of 0.2 mm to0.4 mm. The dimensions of the capillary aperture 221 are such that theedges of the capillary aperture 221 provide a biasing force which actson a capillary element extending through the capillary aperture 221 foradded control of liquid flow to the sonication chamber 219.

In this example, the transducer holder 210 is of liquid silicone rubber(LSR). In this example, the liquid silicone rubber has a Shore A 60hardness. This LSR material ensures that the ultrasonic transducer 215vibrates without the transducer holder 210 dampening the vibrations. Inthis example, the vibratory displacement of the ultrasonic transducer215 is 2-5 nanometres and any dampening effect may reduce the efficiencyof the ultrasonic transducer 215. Hence, this LSR material and hardnessis selected for optimal performance with minimal compromise.

Referring now to FIGS. 16 and 17 , the mist generator device 201comprises a capillary or capillary element 222 for transferring a liquid(containing a drug or other substance) from the liquid chamber 218 tothe sonication chamber 219. The capillary element 222 is planar orgenerally planar with a first portion 223 and a second portion 224. Inthis example, the first portion 223 has a rectangular or generallyrectangular shape and the second portion 224 has a partly circularshape.

In this example, the capillary element 222 comprises a third portion 225and a fourth portion 226 which are respectively identical in shape tothe first and second portions 223, 224. The capillary element 222 ofthis example is folded about a fold line 227 such that the first andsecond portions 223, 224 and the third and fourth portions 225, 226 aresuperimposed on one another, as shown in FIG. 17 .

In this example, the capillary element has a thickness of approximately0.28 mm. When the capillary element 222 is folded to have two layers, asshown in FIG. 17 , the overall thickness of the capillary element isapproximately 0.56 mm. This double layer also ensures that there isalways sufficient liquid on the ultrasonic transducer 215 for optimalaerosol production.

In this example, when the capillary element 222 is folded, the lower endof the first and third parts 223, 225 defines an enlarged lower end 228which increases the surface area of the capillary element 222 in theportion of the capillary element 222 which sits in liquid within theliquid chamber 218 to maximise the rate at which the capillary element222 absorbs liquid.

In this example, the capillary element 222 is 100% bamboo fibre. Inother examples, the capillary element is of at least 75% bamboo fibre.The benefits of using bamboo fibre as the capillary element are asdescribed above.

Referring now to FIGS. 18 and 19 , the capillary element 222 is retainedby the transducer holder 210 such that the transducer holder 210 retainsthe second portion 224 of the capillary element 222 superimposed on partof an atomisation surface of the ultrasonic transducer 215. In thisexample, the circular second portion 224 sits within the internal recess214 of the transducer holder 210.

The first portion 223 of the capillary element 222 extends through thecapillary aperture 221 in the transducer holder 210.

Referring now to FIGS. 20 to 22 , the second portion 206 of the mistgenerator housing 204 comprises a generally circular wall 229 whichreceives the transducer holder 210 and forms part of the wall of thesonication chamber 219.

Contact apertures 230 and 231 are provided in a side wall of the secondportion 206 for receiving electrical contacts 232 and 233 which formelectrical connections with the electrodes of the ultrasonic transducer215.

In this example, an absorbent tip or absorbent element 234 is providedadjacent the mist outlet port 208 to absorb liquid at the mist outletport 208. In this example, the absorbent element 234 is of bamboo fibre.

Referring now to FIGS. 23 to 25 , the first portion 205 of the mistgenerator housing 204 is of a similar shape to the second portion 206and comprises a further generally circular wall portion 235 which formsa further portion of the wall of the sonication chamber 219 and retainsthe transducer holder 210.

In this example, a further absorbent element 236 is provided adjacentthe mist outlet port 208 to absorb liquid at the mist outlet port 208.

In this example, the first portion 205 of the mist generator housing 204comprises a spring support arrangement 237 which supports the lower endof a retainer spring 238, as shown in FIG. 26 .

An upper end of the retainer spring 238 contacts the second portion 224of the capillary element 222 such that the retainer spring 238 providesa biasing force which biases the capillary element 222 against theatomisation surface of the ultrasonic transducer 215.

Referring to FIG. 27 , the transducer holder 210 is shown in positionand being retained by the second portion 206 of the mist generatorhousing 204, prior to the two portions 205, 206 of the mist generatorhousing 204 being attached to one another.

Referring to FIGS. 28 to 31 , in this example, the mist generator device201 comprises an identification arrangement 239. The identificationarrangement 239 comprises a printed circuit board 240 having electricalcontacts 241 provided on one side and an integrated circuit 242 andanother optional component 243 provided on the other side.

The integrated circuit 242 has a memory which stores a unique identifierfor the mist generator device 201. The electrical contacts 241 providean electronic interface for communication with the integrated circuit242.

The printed circuit board 240 is, in this example, mounted within arecess 244 on one side of the mist generator housing 204. The integratedcircuit 242 and optional other electronic components 243 sit within afurther recess 245 so that the printed circuit board 240 is generallyflush with the side of the mist generator housing 204.

In this example, the integrated circuit 242 is a one-time-programmable(OTP) device which provides an anti-counterfeiting feature that allowsonly genuine mist generator devices from the manufacturer to be usedwith the device. This anti-counterfeiting feature is implemented in themist generator device 201 as a specific custom integrated circuit (IC)that is bonded (with the printed circuit board 240) to the mistgenerator device 201. The OTP as IC contains a truly unique informationthat allows a complete traceability of the mist generator device 201(and its content) over its lifetime as well as a precise monitoring ofthe consumption by the user. The OTP IC allows the mist generator device201 to function to generate mist only when authorised.

The OTP, as a feature, dictates the authorised status of a specific mistgenerator device 201. Indeed, in order to prevent emissions of carbonylsand keep the aerosol at safe standards, experiments have shown that themist generator device 201 is considered empty of liquid in the liquidchamber 218 after approximately 1,000 seconds of aerosolisation. In thatway a mist generator device 201 that is not genuine or empty will not beable to be activated after this predetermined duration of use.

The OTP, as a feature, may be part of a complete chain with theconjunction of the digital sale point, the mobile companion applicationand the mist generator device 201. Only a genuine mist generator device201 manufactured by a trusted party and sold on the digital sale pointcan be used in the device. A mobile companion digital app, being a linkbetween the user account on a manufacturer's digital platform and themist generator device 201, ensures safe usage of a known safe contentfor a safe amount of puff duration.

The OTP, as a feature, also enables high access control and monitoringrequired as per medical drug administration in the case of business tobusiness (B2B) use with trusted health establishments. The OTP IC isread by the driver device 202 which can recognise the mist generatordevice 201 inserted and the prescription associated with it. The driverdevice 202 cannot be used with this mist generator device 201 more thannor outside of the time frame specified by the prescription. In additiona reminder on the mobile companion app can be provided to minimise auser missing a dose.

In some examples, the OTP IC is disposable in the same way as the mistgenerator device 201. Whenever the mist generator device 201 isconsidered empty, it will not be activated if inserted into a driverdevice 202. Similarly, a counterfeit generator device 201 would not befunctional in the driver device 202.

FIGS. 32 to 34 illustrate how air flows through the mist generatordevice 201 during operation.

The sonication of the liquid drug (Nicotine, medical solutions, medicalsuspensions, protein solutions, supplements, etc.) transforms it intomist (aerosolisation). However, this mist would settle over theultrasonic transducer 215 unless enough ambient air is available toreplace the rising aerosol. In the sonication chamber 219, there is arequirement for a continuous supply of air as mist (aerosol) isgenerated and pulled out through the mouthpiece to the user. To cater tothis requirement, an airflow channel is provided. In this example theairflow channel has an average cross-sectional area of 11.5 mm², whichis calculated and designed into the sonication chamber 219 based on thenegative air pressure from an average user. This also controls themist-to-air ratio of the inhaled aerosol, controlling the amount of drugdelivered to the user.

Based on design requirements, the air flow channel is routed such thatit initiates from the bottom of the sonication chamber 219. The openingat the bottom of the aerosol chamber aligns with and is tightly adjacentto the opening to an airflow bridge in the device. The air flow channelruns vertically upwards along the reservoir and continues until thecentre of the sonication chamber (concentric with the ultrasonictransducer 215). Here, it turns 90° inwards. The flow path thencontinues on until approximately 1.5 mm from the ultrasonic transducer215. This routing ensures maximised ambient air supplied directly in thedirection of the atomisation surface of the ultrasonic transducer 215.The air flows through the channel, towards the transducer, collects thegenerated mist as it travels out through the mouthpiece and to the user.

The driver device 202 will now be described with reference to FIGS. 35and 36 initially. Air flows into the mist generator device 201 via theair inlet port 207 which, as described below, is in fluid communicationwith an airflow bridge within the driver device 202. The air flows alonga flow path which changes the direction of the air flow by approximately90° to direct the flow of air towards the ultrasonic transducer 215.

In some examples, the airflow arrangement is configured to change thedirection of a flow of air along the air flow path such that the flow ofair is substantially perpendicular to the atomisation surface of theultrasonic transducer as the flow of air passes into the sonicationchamber.

The driver device 202 comprises a driver device housing 246 which is atleast partly of metal. In some examples, the driver device housing 246is entirely of aluminium (AL6063 T6) which protects the internalcomponents from the environment (dust, water splashes, etc.) and alsoprotects from damage from shocks (accidental drops, etc.).

In some examples, the driver device housing 246 is provided with ventson its sides that allow ambient air to enter the device for twopurposes; one to have ventilation around the electronic components andkeep them within operating temperatures, and these vents also act as airinlets with air entering through these vents into the device, and thenthrough the airflow bridge into the mist generator device 201.

The driver device housing 246 is elongate with an internal chamber 247which houses the components of the driver device 202. One end of thedriver device housing 246 is closed by an end cap 248. The other end ofthe driver device housing 247 has an opening 249 which provides anopening for the recess 203 of the driver device 202.

The driver device 202 comprises a battery 250 which is connected to aprinted circuit board 251. In some examples, the battery 250 is a 3.7VDC Li—Po battery with 1140 mAh capacity and 10C discharge rate. The highdischarge rate is required for voltage amplification of up to 15V thatis required by the ultrasonic transducer 215 for desirable operation.The shape and size of the battery is designed, within physicalconstraints, as per the shape and size of the device and space allocatedfor the power source.

The printed circuit board 251 incorporates a processor and a memory andother electronic components for implementing the electrical functions ofthe driver device 202. Charging pins 252 are provided on one end of theprinted circuit board 251 and which extend through the end cap 248 toprovide charging connections to charge the battery 250.

The printed circuit board 251 is retained within the driver devicehousing 246 by a skeleton 252. The skeleton 252 has a channel 253 whichreceives the printed circuit board 251.

The skeleton 252 incorporates raised side portions 254, 255 whichsupport the battery 250.

In some examples, the skeleton 252 is manufactured using industrialinjection moulding processes. The moulded plastic skeleton ensures allparts are fixed and not loosely fitting inside the case. It also forms acover over the front part of the PCB (Printed Circuit Board) whichreceived the mist generator device 201 when it is inserted into thedriver device 202.

The driver device 202 comprises an airflow sensor which acts as a switchfor activating and supplying power to the transducer for sonication andaerosol production. The airflow sensor is mounted onto the PCB in thedevice and requires a certain atmospheric pressure drop around it toactivate the driver device 202. For this, an airflow bridge as shown inFIGS. 39 to 41 is designed with internal channels that direct air fromthe surrounding in through the bridge into the aerosol chamber. Theskeleton 252 comprises opposing channels 256, 257 for receiving portionsof the airflow bridge, as shown in FIG. 42 .

The internal channels in the airflow bridge have a micro-channel (0.5 mmdiameter) that extends down towards a chamber that completely covers theairflow sensor. As the air flows in from the side inlets and upwards tothe aerosol chamber, it creates a negative pressure in the micro-channelthat triggers the airflow sensor to activate the device.

The device is a compact, portable and highly advanced device that allowsprecise, safe and monitored aerosolisation. This is done byincorporating high-quality electronic components designed with IPC class3—medical grade—in mind.

The electronics of the driver device 202 are divided as such:

1. Sonication Section

In order to obtain the most efficient aerosolisation to date forinhalation in a portable device, with particle size below 1 um, thesonication section has to provide the contacts pads receiving theultrasonic transducer 215 (piezoelectrical ceramic disc (PZT)) with highadaptive frequency (approximately 3 MHz).

This section not only has to provide high frequency but also protect theultrasonic transducer 215 against failures while providing constantoptimised cavitation.

PZT mechanical deformation is linked to the AC Voltage amplitude that isapplied to it, and in order to guarantee optimal functioning anddelivery of the system at every sonication, the maximum deformation mustbe supplied to the PZT all the time.

However, in order to prevent the failure of the PZT, the active powertransferred to it must be precisely controlled.

This could only be achieved by designing a custom, not existing in themarket, Power Management Integrated Circuit (PMIC) chip which isprovided on the printed circuit board of the driver device 202. ThisPMIC allows modulation of the active power given to the PZT at everyinstant without compromising the mechanical amplitude of vibration ofthe PZT.

By Pulse Width Modulation (PWM) of the AC voltage applied to the PZT,the mechanical amplitude of the vibration remains the same.

The only ‘on the shelf’ option available would have been to modify theoutput AC voltage via the use of a Digital to Analog Converter (DAC).The energy transmitted to the PZT would be reduced but so would themechanical deformation which as a result completely degrades andprevents proper aerosolisation. Indeed, the RMS voltage applied would bethe same with effective Duty Cycle modulation as with Voltagemodulation, but the active power transferred to the PZT would degrade.Indeed, given the formula below:

Active Power displayed to the PZT being Pα=2√{square root over(2)}/πIrms*Vrms*cos φ,

Where

φ is the shift in phase between current and voltageI_(rms) is the root mean square CurrentV_(rms) is the root mean square Voltage.

When considering the first harmonic, Irms is a function of the realvoltage amplitude applied to the transducer, as the pulse widthmodulation alters the duration of voltage supplied to the transducer,controlling Irms.

The specific design of the PMIC uses a state-of-the-art design, enablingultra-precise control of the frequency range and steps to apply to thePZT including a complete set of feedback loops and monitoring path forthe control section to use.

The rest of the aerosolisation section is composed of the DC/DC boostconverter and transformer that carry the necessary power from a 3.7Vbattery to the PZT contact pads.

The driver device comprises an AC driver for converting a voltage fromthe battery into an AC drive signal at a predetermined frequency todrive the ultrasonic transducer.

The driver device comprises an active power monitoring arrangement formonitoring the active power used by the ultrasonic transducer (asdescribed above) when the ultrasonic transducer is driven by the ACdrive signal. The active power monitoring arrangement provides amonitoring signal which is indicative of an active power used by theultrasonic transducer.

The processor within the driver device controls the AC driver andreceives the monitoring signal drive from the active power monitoringarrangement.

The memory of driver device stores instructions which, when executed bythe processor, cause the processor to:

-   -   A. control the AC driver to output an AC drive signal to the        ultrasonic transducer at a predetermined sweep frequency;    -   B. calculate the active power being used by the ultrasonic        transducer based on the monitoring signal;    -   C. control the AC driver to modulate the AC drive signal to        maximise the active power being used by the ultrasonic        transducer;    -   D. store a record in the memory of the maximum active power used        by the ultrasonic transducer and the sweep frequency of the AC        drive signal;    -   E. repeat steps A-D for a predetermined number of iterations        with the sweep frequency incrementing with each iteration such        that, after the predetermined number of iterations has occurred,        the sweep frequency has been incremented from a start sweep        frequency to an end sweep frequency;    -   F. identify from the records stored in the memory the optimum        frequency for the AC drive signal which is the sweep frequency        of the AC drive signal at which a maximum active power is used        by the ultrasonic transducer; and    -   G. control the AC driver to output an AC drive signal to the        ultrasonic transducer at the optimum frequency to drive the        ultrasonic transducer to atomise a liquid.

In some examples, the active power monitoring arrangement comprises acurrent sensing arrangement for sensing a drive current of the AC drivesignal driving the ultrasonic transducer, wherein the active powermonitoring arrangement provides a monitoring signal which is indicativeof the sensed drive current.

In some examples, the current sensing arrangement comprises anAnalog-to-Digital Converter which converts the sensed drive current intoa digital signal for processing by the processor.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D above with thesweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 2960 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D above with thesweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 3100 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: in step G, control the AC driverto output an AC drive signal to the ultrasonic transducer at frequencywhich is shifted by a predetermined shift amount from the optimumfrequency.

In some examples, the predetermined shift amount is between 1-10% of theoptimum frequency.

2. Control and Information (CI) Section

The Control and Information section comprises an external EEPROM fordata storage, LEDs for user indications, a pressure sensor for airflowdetection and a Bluetooth Low Energy (BLE) capable microcontroller forconstant monitoring and managing of the aerosolisation section.

The pressure sensor used in the device serves two purposes. The firstpurpose is to prevent unwanted and accidental start of the sonic engine(driving the ultrasonic transducer). This functionality is implementedin the processing arrangement of the device, but optimised for lowpower, to constantly measures environmental parameters such astemperature and ambient pressure with internal compensation andreference setting in order to accurately detect and categorise what iscalled a true inhalation.

Unlike all the other e-smoking devices on the market, this solution usesthe strength of a micro-controller to allow the use of only one sensor.

The second purpose of the pressure sensor is to be able to monitor notonly the exact duration of the inhalations by the user for preciseinhalation volume measurement, but also to be able to determine thestrength of the user inhalation which is a critical information inmedical conditions both for proper prescription and health monitoring.All in all, we are able to completely draw the pressure profile of everyinhalation and anticipate the end of an inhalation for bothaerosolisation optimisation and medical data behaviour comprehension.

This was possible with the usage of a Bluetooth™ Low Energy (BLE)microcontroller. Indeed, this enables the setting to provide extremelyaccurate inhalation times, optimised aerosolisation, monitor numerousparameters to guarantee safe misting and prevent the use of non-genuinee-liquids or aerosol chambers and protect both the device againstover-heating risks and the user against over-misting in one shot unlikeany other products on the market.

The use of the BLE microcontroller allows over-the-air update tocontinuously provide improved software to users based on anonymised datacollection and trained AI for PZT modelling.

3. Power Management (PM) Section

The Power Management section is constituted by the 3.7V LiPo batterypath to a low dropout regulator (LDO) that powers the Control andInformation section and a battery management system (BMS) that provideshigh level of protection and charging to the internal LiPo battery.

The components in this section have been selected carefully andthoroughly to be able to provide such an integrated and compact devicewhile providing high power to the sonication section and ensuring asteady powering of the control and information section.

Indeed, when providing high power to the aerosolisation section from a3.7V LiPo battery, the supply voltage varies a lot during operation.Without a low dropout regulator, the Control and Information sectioncould not be powered with a mandatory steady supply when the batteryvoltage drops to as low as 0.3V above the minimum ratings of thecomponents in this section, which is why the LDO plays a crucial rolehere. A loss in the CI section would disturb or even stop thefunctioning of the entire device.

This is why the careful selection of components not only ensures highreliability of the device but also allows it to work under harshconditions and for a longer consecutive time between recharge.

Controlled Aerosolisation

The device is a precise, reliable and a safe aerosolisation solution forboth smoke cessation programs, medical prescription and daily customerusage and, as such, must provide a controlled and trustedaerosolisation.

This is performed through an internal method that can be broken apartinto several sections as follows:

1. Sonication

In order to provide the most optimal aerosolisation the ultrasonictransducer (PZT) needs to vibrate in the most efficient way.

Frequency

The electromechanical properties of piezoelectrical ceramics state thatthe component has the most efficiency at the resonant frequency. Butalso, vibrating a PZT at resonance for a long duration will inevitablyend with the failure and breaking of the component which renders theaerosol chamber unusable.

Another important point to consider when using piezoelectrical materialsis the inherent variability during manufacturing and its variabilityover temperature and lifetime.

Resonating a PZT at 3 MHz in order to create droplets of a size <1 umrequires an adaptive method in order to locate and target the ‘sweetspot’ of the particular PZT inside every aerosol chamber used with thedevice for every single inhalation.

Sweep

Because the device has to locate the ‘sweet spot’ for every singleinhalation and because of over-usage, the PZT temperature varies as thedevice uses an in-house double sweep method.

The first sweep is used when the device has not been used with aparticular aerosol chamber for a time that is considered enough for allthe thermal dissipation to occur and for the PZT to cool down to‘default temperature’. This procedure is also called a cold start.During this procedure the PZT needs a boost in order to produce therequired aerosol. This is achieved by only going over a small subset ofFrequencies between 2900 kHz to 2960 kHz which, considering extensivestudies and experiments, covers the resonant point.

For each frequency in this range, the sonic engine in activated and thecurrent going through the PZT is actively monitored and stored by themicrocontroller via an Analog-to-Digital Converter (ADC), and convertedback to current in order to be able to precisely deduct the Power usedby the PZT.

This yields the cold profile of this PZT regarding frequency and theFrequency used throughout the inhalation is the one that uses the mostcurrent, meaning the lowest impedance Frequency.

The second sweep is performed during any subsequent inhalation and coverthe entire range of frequencies between 2900 kHz to 3100 kHz due to themodification of the PZT profile with regards to temperature anddeformation. This hot profile is used to determine the shift to apply.

Shift

Because the aerosolisation must be optimal, the shift is not used duringany cold inhalation and the PZT will hence vibrate at resonantfrequency. This can only happen for a short and unrepeated duration oftime otherwise the PZT would inevitably break.

The shift however is used during most of inhalations as a way to stilltarget a low impedance frequency, thus resulting in quasi-optimaloperation of the PZT while protecting it against failures.

Because the hot and cold profiles are stored during inhalation themicrocontroller can then select the proper shifted frequency accordingto the measured values of current through the PZT during sweep andensure a safe mechanical operation.

The selection of the direction to shift is crucial as thepiezoelectrical component behaves in a different way if outside theduplet resonant/anti-resonant frequency or inside this range. Theselected shift should always be in this range defined by Resonant toanti-Resonant frequencies as the PZT is inductive and not capacitive.

Finally, the percentage to shift is maintained below 10% in order tostill remain close to the lowest impedance but far enough of theresonance.

Adjustment

Because of the intrinsic nature of PZTs, every inhalation is different.Numerous parameters other than the piezoelectrical element influence theoutcome of the inhalation, like the amount of e-liquid remaining insidethe aerosol chamber, the wicking state of the gauze or the battery levelof the device.

As of this, the device permanently monitors the current used by the PZTinside the aerosol chamber and the microcontroller constantly adjuststhe parameters such as the frequency and the Duty Cycle in order toprovide the aerosol chamber with the most stable power possible within apre-defined range that follows the studies and experimental results formost optimal safe aerosolisation.

Battery Monitoring

In order to provide an AC voltage of 15V and maintain a current insidethe PZT around 2.5A, the current drawn from the battery reaches around 7to 8 Amps, which in turn, creates a drop in the battery voltage. Anycommon LiPo battery would not sustain this demanding resource for theduration of an inhalation that can top 6 s.

This is the reason why a custom LiPo battery is developed that canhandle around 11 Amps, which is 50% more than the maximum allowed in thePZT at all time, while still being simple to use in compact andintegrated portable device.

Because the battery voltage drops and varies a lot when activating thesonication section, the microcontroller constantly monitors the powerused by the PZT inside the aerosol chamber to ensure a proper but alsosafe aerosolisation.

And because the key to aerosolisation is control, the device ensuresfirst that the Control and Information section of the device alwaysfunction and does not stop in the detriment of the sonication section.

This is why the adjustment method also takes into great account the realtime battery level and, if need be, modifies the parameters like theDuty Cycle to maintain the battery at a safe level, and in the case of alow battery before starting the sonic engine, the Control andInformation section will prevent the activation.

Power Control

As being said, the key to aerosolisation is control and the method usedin the device is a real time multi-dimensional function that takes intoaccount the profile of the PZT, the current inside the PZT and thebattery level of the device at all time.

All this is only achievable thanks to the use of a microcontroller thatcan monitor and control every element of the device to produce anoptimal inhalation.

1. Inhalation Control

The device is a safe device and confirmed by BNS (Broughton NicotineServices) report, but in order to guarantee the safety of misting andthe integrity of both the aerosol chamber and the device, eachinhalation has to be controlled.

Inhalation Duration

In order to reduce the exposure to carbonyls and other toxic componentsthat might result from the heating of e-liquid, the maximum duration ofan inhalation is set to 6 seconds which completely ensure that theexposure to these components is contained.

Interval

Because the device relies on a piezoelectrical component, the deviceprevents the activation of the sonication section if an inhalationstops. The safety delay in between two inhalations is adaptive dependingon the duration of the previous one. This allows the gauze to wickproperly before the next activation.

With this functioning, the device can safely operate and theaerosolisation is rendered more optimal with no risk of breaking the PZTelement nor exposing the user to toxic components.

Connectivity (BLE)

The device Control and Information section is composed of a wirelesscommunication system in the form of a Bluetooth Low Energy capablemicrocontroller. The wireless communication system is in communicationwith the processor of the device and is configured to transmit andreceive data between the driver device and a computing device, such as asmartphone.

The connectivity via Bluetooth Low Energy to a companion mobileapplication ensures that only small power for this communication isrequired thus allowing the device to remain functioning for a longerperiod of time if not used at all, compared to traditional wirelessconnectivity solutions like Wi-Fi, classic Bluetooth, GSM or even LTE-Mand NB-IOT.

Most importantly, this connectivity is what enables the OTP as a featureand the complete control and safety of the inhalations. Every data fromresonant frequency of an inhalation to the one used, or the negativepressure created by the user and the duration are stored and transferredover BLE for further analysis and improvements of the embedded software.

Moreover, all these information are crucial when the device is used inmedical or smoke cessation programs because it gives doctors and usersall the information regarding the process of inhalation and the abilityto track in real-time the prescriptions and the usage.

Finally, this connectivity enables the update of the embedded firmwareinside the device and over the air (OTA), which guarantees that thelatest versions can always be deployed rapidly. This gives greatscalability to the device and insurance that the device is intended tobe maintained.

Data Collection for Clinical Smoke Cessation Purposes

The device can collect user data such as number of puffs and puffduration in order to determine the total amount of drug consumed by theuser in a session.

This data can be interpreted by an algorithm that sets consumptionlimits per time period based on a physician's recommendations.

This will allow a controlled therapeutic dose of drug to be administeredto the user that is controlled by a physician or pharmacist and cannotbe abused by the end user.

The physician would be able to gradually lower dosages over time in acontrolled method that is both safe for the user and effective inproviding therapeutic smoke cessation doses.

Puff Limitations

The process of ultrasonic cavitation has a significant impact on thenicotine concentration in the produced mist.

A device limitation of <7 second puff durations will limit the user toexposure of carbonyls commonly produced by electronic nicotine deliverysystems.

Based on Broughton Nicotine Services' experimental results, after a userperforms 10 consecutive puffs of <7 seconds, the total amount ofcarbonyls is <2.67 μg/10 puffs (average: 1.43 μg/10 puffs) forformaldehyde, <0.87 μg/10 puffs (average: 0.50 μg/10 puffs) foracetaldehyde, <0.40 μg/10 puffs (average: 0.28 μg/10 puffs) forpropionaldehyde, <0.16 μg/10 puffs (average: 0.16 μg/10 puffs) forcrotonaldehyde, <0.19 μg/10 puffs (average: 0.17 μg/10 puffs) forbutyraldehyde, <0.42 μg/10 puffs (average: 0.25 μg/10 puffs) fordiacetyl, and acetylpropionyl was not detected at all in the emissionsafter 10 consecutive <7 second puffs.

Because the aerosolisation of the e-liquid is achieved via themechanical action of the piezoelectric disc and not due to the directheating of the liquid, the individual components of the e-liquid(propylene glycol, vegetable glycerine, flavouring components, etc.)remain largely in-tact and are not broken into smaller, harmfulcomponents such as acrolein, acetaldehyde, formaldehyde, etc. at thehigh rate seen in traditional ENDS.

In order to limit the user's exposure to carbonyls while using theultrasonic device, puff length is limited to 6 seconds maximum so thatthe above results would be the absolute worst-case scenario in terms ofexposure.

Referring now to FIGS. 43 and 44 , when the end cap 248 is mounted tothe driver device housing 246, the driver device housing 246, beingaluminium, acts as a Faraday cage, preventing the device from emittingany electromagnetic waves. The device with the driver device housing 246has been tested for Electromagnetic Compatibility (EMC) and the testsreveal that the emissions are less than half the allowed limit fordevices. The EMC test results are shown in the graph of FIG. 45 .

All of the above applications involving ultrasonic technology canbenefit from the optimisation achieved by the frequency controller whichoptimises the frequency of sonication for optimal performance.

It is to be appreciated that the disclosures herein are not limited touse for nicotine delivery. Some examples are configured for use forvarious medical purposes (e.g. the delivery of CBD for pain relief,supplements for performance enhancement, albuterol/salbutamol for asthmapatients, etc.)

The devices disclosed herein are for use with any drugs or othercompounds, with the drug or compound being provided in a liquid withinthe liquid chamber of the device for aerosolisation by the device. Insome examples, the devices disclosed herein are for use with drugs andcompounds including, but not limited to, the following:

-   -   Respiratory    -   Brochodilators    -   Olodaterol    -   Levalbuterol    -   Berodual (Ipratropium bromide/Fenoterol)    -   Combivent (Ipratropium bromide/Salbutamol)    -   Anti-inflammatory    -   Betamethasone    -   Dexamethasone    -   Methylprednisolone    -   Hydrocortisone    -   Mucolytics    -   N-Acetylcysteine    -   Pulmonary Hypertension    -   Sildenafil    -   Tadalafil    -   Epoprostenol    -   Treprostenil    -   Iloprost    -   Infectious Disease    -   Antimicrobials    -   Aminoglycosides (Gentamicin, Tobramycin, Amikacin, Colomycin,        Neomycin, Liposomal Amikacin,)    -   Quinolones (Ciprofloxacin, Levofloxacin, Moxifloxacin Ofloxacin)    -   Macrolides (Azithromycin)    -   Minocycline    -   Betalactams (Piperacillin-Tazobactam, Ceftazidime Ticarcillin)    -   Cephalosporins (Cefotaxime, Cefepime, Ceftriaxone, Cefotaxime)    -   Glycopeptides (Vancomycin)    -   Meropenem    -   Polymixin (Colistin, Polymixin B)    -   Antifungels    -   Amphotericin    -   Fluconazole    -   Caspofungen    -   Antivirals    -   Valganciclovir    -   Favipiravir    -   Remdisivir    -   Acyclovir    -   Anti TB    -   Isoniazid    -   Pyrazinamide    -   Rifampin    -   Ethambutol    -   Oncology    -   Biologics    -   Gilotrif    -   Afatinib    -   Caplacizumab    -   Dupilumab    -   Isarilumab    -   Alirucomab    -   Volasertib    -   Nintedanib    -   Imatinib    -   Sirolimus    -   Chemotherapy    -   Azacitidine    -   Decitabine    -   Docetaxel    -   Gemcitabine    -   Cisplatinum    -   CNS & PSYCH    -   Sodium valproate    -   Teriflunomide    -   Zomitriptan    -   METABOLIC/HORMONAL    -   Insulin    -   Estrogen    -   IMMUNOLOGY    -   Vaccine    -   Monoclonal Antibodies    -   Stem Cells    -   Vitamins    -   Zinc    -   Ascorbic Acid    -   Miscellaneous    -   Niclosamide    -   Hydroxychloroquine    -   Ivermectin

The ultrasonic mist inhaler 100 of some examples is a more powerfulversion of current portable medical nebulizers, in the shape and size ofcurrent e-cigarettes and with a particular structure for effectivevaporization. It is a healthier alternative to cigarettes and currente-cigarettes products.

The ultrasonic mist inhaler 100 of some examples has particularapplicability for those who use electronic inhalers as a means to quitsmoking and reduce their nicotine dependency. The ultrasonic mistinhaler 100 provides a way to gradually taper the dose of nicotine.

Other examples of the ultrasonic mist inhaler devices are easilyenvisioned, including medicinal delivery devices.

The foregoing outlines features of several examples or embodiments sothat those of ordinary skill in the art may better understand variousaspects of the present disclosure. Those of ordinary skill in the artshould appreciate that they may readily use the present disclosure as abasis for designing or modifying other processes and structures forcarrying out the same purposes and/or achieving the same advantages ofvarious examples or embodiments introduced herein. Those of ordinaryskill in the art should also realise that such equivalent constructionsdo not depart from the spirit and scope of the present disclosure, andthat they may make various changes, substitutions, and alterationsherein without departing from the spirit and scope of the presentdisclosure.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter of the appended claims is not necessarily limited tothe specific features or acts described above. Rather, the specificfeatures and acts described above are disclosed as example forms ofimplementing at least some of the claims.

Various operations of examples or embodiments are provided herein. Theorder in which some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated having the benefitof this description. Further, it will be understood that not alloperations are necessarily present in each embodiment provided herein.Also, it will be understood that not all operations are necessary insome examples or embodiments.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication and the appended claims are generally be construed to mean“one or more” unless specified otherwise or clear from context to bedirected to a singular form. Also, at least one of A and B and/or thelike generally means A or B or both A and B. Furthermore, to the extentthat “includes”, “having”, “has”, “with”, or variants thereof are used,such terms are intended to be inclusive in a manner similar to the term“comprising”. Also, unless specified otherwise, “first,” “second,” orthe like are not intended to imply a temporal aspect, a spatial aspect,an ordering, etc. Rather, such terms are merely used as identifiers,names, etc. for features, elements, items, etc. For example, a firstelement and a second element generally correspond to element A andelement B or two different or two identical elements or the sameelement.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others of ordinary skill in the art based upon a readingand understanding of this specification and the annexed drawings. Thedisclosure comprises all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described features(e.g., elements, resources, etc.), the terms used to describe suchfeatures are intended to correspond, unless otherwise indicated, to anyfeatures which performs the specified function of the described features(e.g., that is functionally equivalent), even though not structurallyequivalent to the disclosed structure. In addition, while a particularfeature of the disclosure may have been disclosed with respect to onlyone of several implementations, such feature may be combined with one ormore other features of the other implementations as may be desired andadvantageous for any given or particular application.

Examples or embodiments of the subject matter and the functionaloperations described herein can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this specification and their structuralequivalents, or in combinations of one or more of them.

Some examples or embodiments are implemented using one or more modulesof computer program instructions encoded on a computer-readable mediumfor execution by, or to control the operation of, a data processingapparatus. The computer-readable medium can be a manufactured product,such as hard drive in a computer system or an embedded system. Thecomputer-readable medium can be acquired separately and later encodedwith the one or more modules of computer program instructions, such asby delivery of the one or more modules of computer program instructionsover a wired or wireless network. The computer-readable medium can be amachine-readable storage device, a machine-readable storage substrate, amemory device, or a combination of one or more of them.

The terms “computing device” and “data processing apparatus” encompassall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, aruntime environment, or a combination of one or more of them. Inaddition, the apparatus can employ various different computing modelinfrastructures, such as web services, distributed computing and gridcomputing infrastructures.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto-optical disks, or optical disks. However, a computerneed not have such devices. Devices suitable for storing computerprogram instructions and data include all forms of non-volatile memory,media and memory devices.

In the present specification “comprise” means “includes or consists of”and “comprising” means “including or consisting of”.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

1. A driver device for a mist inhaler device, the driver devicecomprising: a battery; an AC driver for converting a voltage from thebattery into an AC drive signal at a predetermined frequency to drive anultrasonic transducer; an active power monitoring arrangement formonitoring the active power used by the ultrasonic transducer when theultrasonic transducer is driven by the AC drive signal, wherein theactive power monitoring arrangement provides a monitoring signal whichis indicative of an active power used by the ultrasonic transducer; aprocessor for controlling the AC driver and for receiving the monitoringsignal drive from the active power monitoring arrangement; and a memorystoring instructions which, when executed by the processor, cause theprocessor to: A. control the AC driver to output an AC drive signal tothe ultrasonic transducer at a predetermined sweep frequency; B.calculate the active power being used by the ultrasonic transducer basedon the monitoring signal; C. control the AC driver to modulate the ACdrive signal to maximise the active power being used by the ultrasonictransducer; D. store a record in the memory of the maximum active powerused by the ultrasonic transducer and the sweep frequency of the ACdrive signal; E. repeat steps A-D for a predetermined number ofiterations with the sweep frequency incrementing with each iterationsuch that, after the predetermined number of iterations has occurred,the sweep frequency has been incremented from a start sweep frequency toan end sweep frequency; F. identify from the records stored in thememory the optimum frequency for the AC drive signal which is the sweepfrequency of the AC drive signal at which a maximum active power is usedby the ultrasonic transducer; and G. control the AC driver to output anAC drive signal to the ultrasonic transducer at the optimum frequency todrive the ultrasonic transducer to atomise a liquid; and a currentsensing arrangement for sensing a drive current of the AC drive signaldriving the ultrasonic transducer, wherein the active power monitoringarrangement provides a monitoring signal which is indicative of thesensed drive current.
 2. The driver device of claim 1, wherein thememory stores instructions which, when executed by the processor, causethe processor to: repeat steps A-D with the sweep frequency beingincremented from a start sweep frequency of 2900 kHz to an end sweepfrequency of 2960 kHz.
 3. The driver device of claim 1, wherein thememory stores instructions which, when executed by the processor, causethe processor to: repeat steps A-D with the sweep frequency beingincremented from a start sweep frequency of 2900 kHz to an end sweepfrequency of 3100 kHz.
 4. The driver device of claim 1, wherein thememory stores instructions which, when executed by the processor, causethe processor to: in step G, control the AC driver to output an AC drivesignal to the ultrasonic transducer at frequency which is shifted bybetween 1-10% of the optimum frequency.
 5. The driver device of claim 1,wherein the driver device further comprises: a wireless communicationsystem which is in communication with the processor, the wirelesscommunication system being configured to transmit and receive databetween the driver device and a computing device.
 6. The driver deviceof claim 1, wherein the AC driver modulates the AC drive signal by pulsewidth modulation to maximise the active power being used by theultrasonic transducer.
 7. The driver device of claim 1, wherein thedriver device is releasably attached to a mist generator device suchthat the driver device is separable from the mist generator device.